1. Field of the Invention
The present invention relates to a circuit-mounted board to be inserted into an expansion slot of a data processing apparatus such as a computer system, more particularly to a load adjustment board capable of adjusting a load value thereof.
2. Related Art
FIG. 4 shows a conventional memory module to be inserted into a memory expansion slot of a computer system or the like. The memory module 20 has a plurality of memory ICs 25 mounted on a printed circuit having a multi-layered structure. A contact 21 and each pin 25a of the memory IC 25 are electrically connected to each other via internal wiring of the printed circuit or external wiring 27.
FIG. 5 shows the motherboard of the computer system in which the memory modules 20 are inserted. On the motherboard 52 with a multi-layered structure, a memory controller 54 and a plurality of sockets 38a for memory module are mounted. Each memory module 20 is inserted into a socket 38a. The memory controller 54 and the sockets 38a are connected via internal wiring or external wiring 52a so as to carry electric signals between the memory controller 54 and the memory ICs 25.
In the computer system shown in. FIG. 5, when there is a vacant slot X of the slots 38a on the motherboard 52 to which no memory module 20 is connected, the extremely light-weight load on the signal line of the vacant slot X may cause the system to malfunction due to undesired high frequency reflection noise or the like. This sometimes becomes a problem in the reliability of the operations of the system.
The present invention has been contrived to solve the above-mentioned problem, and has an object of providing a board mounted with circuits and capable of improving the reliability in the operations of the system having expansion slots.
A load adjustment board according to the present invention is a board mounted with circuits and is to be inserted into an expansion slot of a data processing apparatus. The load adjustment board comprises a plurality of connection pins to obtain electric connection in the expansion slot, and devices each having variable electric properties. Each of the devices is provided for one of the plurality of connection pins. The one end of the device is connected to the one of the plurality of connection pins, and the other end of the device is connected to a node which supplies a predetermined potential.
Thus, the insertion of the load adjustment board according to the present invention into the expansion slot can eliminate undesired high frequency components on the signal line of the slot and reduce reflection noise, thereby improving the reliability in the operations of the data processing apparatus.
In the load adjustment board, the device may comprise a variable resistor, a variable capacitor, or a combination of these. By using such an electrical property variable device, the load on the signal line can be adjusted in accordance with the drivability of the memory controller or the load of the memory modules.
The predetermined potential may be a ground potential. Fixing to the ground potential can cut off undesired high frequency components on the signal line of the slot to reduce reflection noise.
The load adjustment board may further comprise means for adjusting a length of wiring between the device and the connection pin. Thus the load on the signal line can be finely adjusted.
A data processing apparatus according to the present invention comprises an expansion slot into which a board for expanding function of the device is inserted, and the load adjustment board which is inserted into the expansion slot. In the data processing apparatus, the expansion slot may be a memory expansion slot.
According to the data processing apparatus of the present invention, inserting the above-described load adjustment board into an expansion slot such as a memory expansion slot cuts off undesired high frequency components on the signal line of the slot, and reflection noise, thereby improving the reliability in the operations of the device.